1. Field of the Invention
The present invention relates to the field of disk drives, and in particular, to a microactuator for finely positioning a read/write head of a hard disk drive and a suspension arrangement of the hard disk with the microactuator.
2. Description of the Related Art
A disk drive is an information storage device that uses a rotatable disk with data tracks, a magnetic head (SLD [slider]) for reading or writing data from or onto the tracks, and an actuator connected to a carrier for moving the head across the disk. A servo system receives prerecorded positioning information read from the disk by the head, and sends control signals to the actuator to move the head to the desired track and keep following it when the head is flying.
The SLD flying over information tracks of the disks is mounted on a suspension of the actuator, which has a load beam with a base plate on one end (proximal end), and a flexure on the other end (distal end) on one end (proximal end), and a flexure on tile other end (distal end) on which the SLD is located. There is a spring region near the base plate on the load beam, the thickness of which is thinner than that of other areas, producing a force to help maintain the flying SLD stability. The base plate of the suspension is mounted to the actuator arm, which is controlled by the servo system to position the SLD. A similar mechanism for minute movement of a head used in a disk drive is disclosed in U.S. Pat. No. 5,764,444 issued on Jun. 9, 1998, to Takahiro Imamura et al, and assigned to Fujitsu Limited. However, this mechanism is unable to precisely control the displacement of the head with a high efficiency.
Since the disk storage capacity is increasing all of the time, it becomes more difficult for the actuator and servo system to position the SLD over the desired track quickly and accurately. Many kinds of microactuator or fine tracking motors have been developed to overcome these problems, which are called as dual stage systems since the microactuators are added to the suspensions and will work with the previous actuators together.
Recently, piezoelectric materials are used more and more in microactuators that can extend or contract under a certain voltage with high efficiency. There are two kinds of suspension arrangements for the piezoelectric microactuator in current dual stage servo system designs. One is suspension type: the microactuator is mounted on the proximal end of the suspension (near the spring region); another is SLD type: the microactuator is mounted on the distal end of the suspension, between the SLD and flexure (called a piggy back design).
The challenges in microactuator design on the suspension are: the SLD should get a big lateral displacement under control of the dual stage servo system, the suspension assembly with a microactuator should keep the resonance frequency as high as possible and the strength as strong as possible and should not affect the SLD flying.
One object of the present invention is to provide a new kind of design of a microactuator with piezoelectric materials that can be used on both suspension type and piggy back type designs.
Another object of the present invention is to provide a new kind of suspension arrangement for suspension type design with this kind of microactuator, with a high lateral displacement and a high resonance frequency.
The microactuator of an embodiment in accordance with the present invention includes two active arms, each including a circular part and a straight part, with a symmetrical arrangement, with one or more layers of piezoelectric materials in the structure. They are built in one body with connection by two parts, called connection bodies, at the two ends of the two arms respectively. The two active arms are connected to the two electric pads. When certain voltages of opposite polarities are applied to the two pads, one arm contracts while the other extends in their length direction. If one connection body is fixed as a fixed end, it will produce a moment and cause a rotary movement on the circular part of the arms and a deflection on the straight part of the arms so that the other connection body, as a free end, will get a big deflection along a tracking axis.
For suspension type microactuators, the embodiment of the suspension arrangement of this kind of design includes a load beam having a rigid body with a proximal end and a distal end. The proximal end of the load beam includes a base plate and a spring region nearby on the load beam. A flexure includes two parts: one is body connected to the rigid body of the load beam, the other is a distal end connected to the distal end of the load beam by welding. A read/write head (SLD), located on the distal end of the flexure at the distal end of the load beam. There is a connection region on the load beam to connect the rigid body and the distal end, and there is also a connection region on the flexure to connect the body and the distal end, which are designed to easily make the distal ends move laterally. There is a rotary piezoelectric microactuator on the connection region of the load beam or flexure, which connects the rigid body to the distal end of the load beam as well. When a voltage is applied, the microactuator will drive the distal end of the load beam to deflect along a tracking axis with the SLD.
For the piggy back type, the embodiment design includes a suspension with a load beam and a flexure assembly, a SLD, a rotary piezoelectric microactuator that is connected to the SLD at one end, and to the flexure at the other end with epoxy or other bonding agent, on the distal end of the load beam. When a voltage is applied, the microactuator will drive the SLD to deflect along a tracking axis.